As the reserves of conventional crude oils decline, heavy oils must be upgraded to meet world demands. In heavy oil upgrading, heavier materials are converted to lighter fractions and most of the sulfur, nitrogen and metals must be removed. Heavy oils include materials such as petroleum crude oil, atmospheric tower bottoms products, vacuum tower bottoms products, heavy cycle oils, shale oils, coal derived liquids, crude oil residuum, topped crude oils and the heavy bituminous oils extracted from oil sands. These heavy hydrocarbon feedstocks may be characterized by low reactivity in visbreaking, high coking tendency, poor susceptibility to hydrocracking and difficulties in distillation. Most residual oil feedstocks which are to be upgraded contain some level of asphaltenes which are typically understood to be heptane insoluble compounds as determined by ASTM D3279 or ASTM D6560. Asphaltenes are high molecular weight compounds containing heteroatoms which impart polarity.
Heavy oils must be upgraded in a primary upgrading unit before they can be further processed into useable products. Primary upgrading units known in the art include, but are not restricted to, coking processes, such as delayed or fluidized coking, and hydrogen addition processes such as ebullated bed or slurry hydrocracking (SHC).
In SHC, a three-phase mixture of heavy liquid oil feed cracks in the presence of gaseous hydrogen over solid catalyst particles (e.g., as a particulate metallic compound such as a metal sulfide) in a slurry phase to produce lighter products under pressure at an elevated temperature. Representative slurry hydrocracking processes are described, for example, in U.S. Pat. Nos. 5,755,955 and 5,474,977.
Some SHC catalysts may agglomerate in later reactors which reduces their effectiveness.
Thus, there is a need for methods of reducing the agglomeration of SHC catalysts.